1. Field of Invention
This invention is directed to apparatus and methods that compensate for show-through of images from a back side of a translucent image bearing substrate when scanning the images.
2. Description of Related Art
When a user wishes to reproduce an image on an image bearing substrate or obtain an electronic version of the image on the image bearing substrate, the image bearing substrate on which the image is formed is passed within a detection field of an optical sensor. The passing of the image bearing substrate within the detection field of the optical sensor is termed "scanning" the image bearing substrate. The optical sensor detects light reflected from the surface of the image bearing substrate and obtains data representing the reflected light. The data obtained is an electronic representation of the images formed on the image bearing substrate, because the colors and shadings of the images on the image bearing substrate reflect different amounts and wavelengths of light.
When a double-sided translucent image bearing substrate, having images on both sides of the image bearing substrate, is scanned, the electronic representation generated by scanning one side of the image bearing substrate will contain information from both sides of the image bearing substrate due to light passing through the image bearing substrate. The high contrast image information of the scanned side, or front, of the image bearing substrate will be combined with the low contrast image information from the back side of the image bearing substrate. This low contrast image information from the back side of the image bearing substrate is called "show-through" image information.
One way in which show-through image information is reduced is to place a black backing on the back side of the image bearing substrate during scanning. The light that passes through the image bearing substrate is absorbed by the black backing. Although there is a significant reduction of the show-through image information, there is a small residual low contrast image of the back side remaining in the scanned image due to light scattering off the back side of the image bearing substrate.
Additionally, this method is undesirable because with a black backing any perforations in the image bearing substrate and regions beyond the edges of the image bearing substrate appear as black regions in the scanned image.